Adsorbers, in particular NOx adsorbers, are known. Referred to as LNT, short for lean NOx traps, these adsorbers remove nitrogen oxides (NOx) from exhaust gases of internal combustion engines. NOx adsorbers have, inter alia, an adsorption means, for example barium oxide and/or other oxides and/or carbonates and bind chemically nitrogen oxides from an exhaust gas of the internal combustion engine in a lean operating mode of the internal combustion engine. Adsorbers are, in particular, installed in the coating of a catalytic converter. If the capacitance of the adsorber is saturated, it is regenerated in a phase in which the internal combustion engine is operated in a rich fashion, and the released NOx is reduced to nitrogen by means of the catalytic converter. A method for rinsing an NOx adsorber is described, for example, in DE 102 49 017 A1.
In addition, hybrid drives with a combination of an internal combustion engine and at least one electric machine are also known in motor vehicle engineering.
An object of the present description is to improve regeneration methods of the abovementioned type with the aid of hybrid technology.
The regeneration method according to the description serves to regenerate an adsorber, connected downstream of an internal combustion engine, of a motor vehicle with a hybrid drive train. The internal combustion engine is operated in a phase of rich combustion for regeneration of the adsorber. According to the description, for the rich combustion an engine load and/or an engine rotational speed of the internal combustion engine is influenced by means of an electric machine which can be coupled mechanically to the internal combustion engine. It is therefore advantageously possible to influence the running of the internal combustion engine with respect to the rich combustion according to demand.
In one advantageous refinement, the description provides that in at least one mode in the regeneration method an initial operating point of the internal combustion engine which is in a range which is unsuitable for the rich combustion is shifted to a target operating point in an operating range which is suitable for the rich combustion. It is therefore advantageously not necessary to wait for an operating state which is suitable for the rich operating mode, but instead it can be selectively brought about, independently of the initial operating state of the internal combustion engine. Regeneration is therefore possible more frequently and more appropriately in terms of demand. The adsorber can therefore be more easily placed in a regenerated state, and further exhaust gas components are therefore better available for the adsorption.
In one particular refinement of the regeneration method according to the description there is provision that in a first mode an initial operating point of the internal combustion engine which is in a range of excessively low engine load, which is unsuitable for the rich combustion, is shifted to a target operating point in an operating range which is suitable for the rich combustion by virtue of the fact that the internal combustion engine additionally drives the electric machine as a generator. The engine load is therefore additionally increased. In particular, the electric machine recharges, as a generator, an accumulator here.
Conversely, in a further particular refinement of the regeneration method according to the description there is provision that in a second mode an initial operating point of the internal combustion engine which is in a range of excessively high engine load, which is unsuitable for the rich combustion, is shifted to the target operating point in the operating range by virtue of the fact that an electric machine is additionally operated as a motor in parallel with the internal combustion engine, and the engine load is therefore decreased.
As a result, operating states of the internal combustion engine, in which otherwise no regeneration could take place owing to unfavorable engine loads, can be specifically compensated for.
In one further particular refinement of the regeneration method according to the description there is provision that in a third mode an initial operating point of the internal combustion engine which is in a range of excessively low engine rotational speed, which is unsuitable for the rich combustion, is shifted to the target operating point in the operating range by virtue of the fact that the engine rotational speed is increased.
Conversely, in a further particular refinement of the regeneration method according to the description there is provision that in a fourth mode an initial operating point of the internal combustion engine which is in a range of excessively high engine rotational speed, which is unsuitable for the rich combustion, is shifted to the target operating point in the operating range by virtue of the fact that the engine rotational speed is decreased. As a result, operating states of the internal combustion engine, in which otherwise no regeneration could take place owing to unfavorable engine rotational speeds, can be specifically compensated for.
In a further particular refinement of the regeneration method according to the description there is provision that in a fifth mode an initial operating point of the internal combustion engine which is in an operating range, which is suitable for the rich combustion, is shifted to a target operating point at a location in the operating range which is optimum for the rich combustion by virtue of the fact that the engine rotational speed is decreased or increased and/or the engine load is decreased or increased.
It is therefore advantageously possible to carry out the regeneration in an optimum range of the operating range. As a result, disadvantages such as excessively high fuel consumption, thinning of the engine oil, excessively high CO2 emissions and smoke emissions can be avoided. Stable running of the engine compared to non-optimum operating points is also ensured here. Furthermore, excessively high exhaust gas temperatures can be advantageously avoided in order to protect the exhaust gas turbocharger and the exhaust gas post-treatment systems connected downstream.
In a further particular refinement of the regeneration method according to the description there is provision that in a sixth mode torque of the internal combustion engine is compensated during the rich combustion by torque of the electric machine operated in the engine operating mode. In particular, the sixth mode is carried out subsequent to the other modes if the target operating point is reached. As a result, fluctuations in the torque of the internal combustion engine during the rich combustion can be advantageously compensated for. The motor vehicle carries on running uniformly without adverse effects on comfort.
The regeneration method according to the description is preferably applied in a motor vehicle. The motor vehicle has at least one electric machine, one accumulator, which is electrically connected to the electric machine, one internal combustion engine which can be mechanically coupled to the or one electric machine by means of a distributor unit, one adsorber which is connected downstream of the internal combustion engine, and one management unit. The motor vehicle according to the description is designed to carry out the method according to the description.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.